Tizanidine is a muscle relaxant. It has antispasmodic and antispastic effects, meaning that it targets the skeletal muscles and central nervous system to improve muscle tightness and reduce muscle spasms. A doctor may prescribe tizanidine to manage spasticity resulting from various conditions, including multiple sclerosis, stroke, and spinal cord injuries.

Although people usually tolerate tizanidine well and find that it can provide relief, muscle relaxants can sometimes cause side effects. Therefore, it is important that people follow the dosage that their doctor recommends.

Generally, doctors will recommend that people start at 2 milligrams (mg) per dose and gradually increasing this amount until they get optimal relief. If necessary, individuals may take the medication three times per day — with 6–8 hours between doses — but the dosage should not exceed 36 mg a day.

Common side effects of tizanidine include dry mouth, drowsiness, fatigue, and dizziness. The main warnings associated with the drug are the risk of low blood pressure and liver damage.

In this article, we discuss tizanidine in more detail, including its uses, dosage, side effects, and drug interactions.

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Tizanidine belongs to a class of drugs called central alpha-2 adrenergic receptor agonists. It is a fast-acting muscle relaxant that doctors commonly prescribe to help manage muscle spasticity.

It works by increasing the inhibition of motor neurons in the brain, which are the nerve cells that send messages to muscles to contract. Although the drug has no direct effect on muscles, its inhibition of motor neurons indirectly causes the muscles to relax.

Doctors may use tizanidine to manage muscle spasms that occur due to the following:

Tizanidine is available in the form of 2- or 4-mg tablets and 2-, 4-, or 6-mg capsules. The Food and Drug Administration (FDA) notes that a single dose of 8 mg can relieve spasticity for several hours. The effects are highest at 1–2 hours post-dose, and they end after roughly 3–6 hours.

People will typically start on a lower dose of 2 or 4 mg due to the possible dose-related side effects. A doctor can then increase the dose in increments of 2–4 mg every 1–4 days to achieve the optimal effect possible with a tolerable amount of side effects. People can repeat the dose at 6–8 hour intervals, but they should never exceed three doses, or a total of 36 mg, in 24 hours.

It is also worth noting that doctors may use tizanidine with caution in people with liver or kidney impairments, as these issues may decrease the rate of clearance and lead to the drug having a more prolonged effect on the body.

The most common side effects include:

  • dry mouth
  • dizziness
  • urinary tract infections
  • constipation
  • sleepiness and lethargy
  • weakness and lack of energy
  • vomiting
  • speech disorders
  • urinary frequency
  • blurred vision
  • nervousness
  • flu syndrome, which is a cluster of symptoms similar to those of the flu
  • abnormal liver function test results
  • inflammation of the mucous membranes of the nose
  • sore throat
  • involuntary movements

A 2021 research article warns against taking tizanidine with fluvoxamine (Luvox), a medication for obsessive-compulsive disorder, or ciprofloxacin (Cipro), an antibiotic. Either of these combinations may result in low blood pressure or problems with involuntary movements.

It is also not advisable to take tizanidine with other CYP1A2 inhibitors, such as birth control pills, due to the possible drug interactions. CYP1A2 is an enzyme that helps metabolize drugs. If CYP1A2 inhibition occurs, the body will not be able to clear the drug efficiently, which increases the likelihood of adverse reactions.

Evidence also suggests that tizanidine may interact with alcohol, other central nervous system depressants, such as opioids, and other central alpha-2 adrenergic agonists.

Possible risks associated with tizanidine include:

  • Liver injury: Clinical studies have shown that about 5% of people who take tizanidine have elevations of liver enzymes up to more than three times the upper limit of normal. In most cases, the enzymes return to normal upon discontinuing the drug. However, there have been occasional reports of symptoms of liver damage and rare reports of deaths from this effect.
  • Low blood pressure: Doctors should watch for signs and symptoms of this condition, such as lightheadedness, dizziness, a slow heartbeat, and fainting.
  • Sedation: Clinical studies suggest that 48% of individuals taking tizanidine experience sedation, or drowsiness. In 10% of cases, sedation is likely to be severe.
  • Hallucinations: In two clinical studies, 3% of people who took tizanidine experienced hallucinations or delusions. Hallucinations involve seeing, hearing, tasting, smelling, or feeling something that is not present. A delusion is a belief in something that is not true.

Timing and food can make a difference when taking tizanidine. Also, if it becomes necessary to discontinue the drug, the way in which a person does this is important.

Due to the short duration of effect, people should take tizanidine when a reduction in spasticity is most important. If a person accidentally misses a dose, they should skip it if it is almost time for the next dose. Not allowing 6–8 hours to pass between doses may result in an overdose.

The effect of food on tizanidine is complex and can differ depending on whether a person is taking a tablet or capsule. Food can increase some aspects of absorption for tablets but decrease absorption for capsules. Due to this, it may result in a higher likelihood of adverse events or more rapid or delayed effects of the drugs.

Therefore, it is vital for people to follow their doctor’s instructions on how to take the drug, including whether to take it with or without food.

If someone discontinues tizanidine, they should do so slowly, particularly if they are taking high dosages. Reducing the dosage gradually can help decrease the risk of withdrawal or other adverse effects, such as high blood pressure or rapid heartbeat. A doctor will explain the best way to taper off the drug.

Additional considerations may involve storage, insurance, and monitoring for toxic effects.

Storage

The FDA states that the ideal storage temperature is 77°F (25°C) but that 59–86°F (15–30°C) is ok for a limited time. Pharmacists should dispense the drug in a container with a child-resistant cap.

Insurance

Most private insurers and Medicare plans cover tizanidine, but the copay and deductible vary with the policy. Without insurance, anecdotal evidence suggests that the average cost of a 30-count prescription of 4-mg tablets is close to $20.

Monitoring

When people take tizanidine, it is important for a doctor to monitor kidney and liver function, particularly before increasing the dosage. Typically, this monitoring will involve:

  • measuring creatinine, which is a waste product that indicates how well the kidneys are working
  • liver function tests, which measure liver enzyme levels and can help identify potential damage to the liver
  • watching for symptoms of low blood pressure

Doctors may prescribe tizanidine to relieve the muscle spasticity that can affect people with conditions such as multiple sclerosis. The drug inhibits motor neurons, which allows the muscles to relax. It is available in tablet and capsule formulations.

As tizanidine may cause side effects, it is important that people follow the dosage that their doctor recommends. The drug is available in strengths of 2, 4, and 6 mg.

People can take up to three doses a day, but these should be 6–8 hours apart, and the total dosage over 24 hours should not exceed 36 mg. People should also make their doctor aware of any other medications that they are currently taking and ask whether they should take tizanidine with food.